Thursday, December 29, 2016

4 Things You Didn’t Know About an Ectomycorrhizal Fungi. Number 3 Will Shock You (or Not)!

by AT

When
talking about fungi, many people first think about mushrooms like the brown
Portabellas that we use in cooking (which are actually just a matured version
of the white mushrooms). But wait, there’s more! Besides mushrooms, there are
other types of fungi. For example, there are fungi that actually form a symbiotic
relationship with plants! Like a cat and its owner, symbiosis involves two
different species doing good things for each other despite not needing each
other. Some of these symbiotic fungi associate with plant roots and are called
ectomycorrhizal fungi. In these relationships, the ectomycorrhizal fungi
scavenge for nutrients and share these nutrients with their hosts in exchange
for carbon fixed by plant photosynthesis.6 With that, here are five
things you didn’t know (to be honest, you probably didn’t know it even existed)
about an ectomycorrhizal fungi called Cenococcum
geophilum (C. geophilum).

1. C. geophilum had several other names
before. Talk about an identity crisis…

Although C. geophilum is the official name for the species, it has
historically been called other names such as Lycoperdon graniforme and Cenococcum
graniforme.3 It was first named Lycoperdon graniforme by James Sowerby in 1800. In 1825, Elias
Fries introduced the genus name of Cenococcum,
replacing Lycoperdon. Several years
later, the name C. geophilum was
introduced, however, it was still interchangeable with Cenococcum graniforme for many years before C. geophilum was established as the official name. Finally.

2. Got trees? C. geophilum can form symbiotic relationships
with many different hosts in different places.

C. geophilum can
pretty much grow anywhere. Other common ectomycorrhizal usually associate with
just one plant host, but C. geophilum
is known to associate with any plant that is capable of hosting ectomycorrhizal
fungi. However, it is most commonly found in temperate forests.7 You
can generally find C. geophilum
growing on the roots of various pine, oak, birch, willow, and aspen trees all
over Europe and North America. Also, it is commonly found as far north as the
tundra of northern Alaska and as far south as Florida.7 Wet or dry soils,
this fungus can take it all. Under conditions that aren’t looking too good, C. geophilum can form sclerotia, which
are large masses of hardened mycelium that are resistant to harsh environmental
conditions.3 In C. geophilum,
the sclerotia are known to survive for several years. When there are more
sunshine and rainbows, the sclerotia germinate to reestablish fungal communities.
With such an ability to grow in different regions, it would be no surprise to
find this fungus in other areas around the world like the tropics. In fact,
it’s been found in Puerto Rico!7 Look no further for the fungal
jack-of-all-trades.

3. C. geophilum could be very important to
establishing forests. Stunning, tree-mendous, forests.

Because C. geophilum is a very common
ectomycorrhizal fungus, it has also been well studied since its discovery in
1800. An interesting recent discovery was how the production of melanin, a
complex dark polymer, in the cell walls of hyphae helps the fungus resist dry
conditions.2 If an ectomycorrhizal fungus is resistant to drought
conditions, then this resistance probably benefits the survival of the host
tree as well. As an example, if the ectomycorrhizal fungus dies during a
drought, the tree can survive, but it essentially becomes widowed. Then, the poor
tree will need to establish a new relationship with an ectomycorrhizal fungus
to obtain the nutrients provided by the previous symbiotic relationship. Otherwise,
the tree can’t get enough water, and it could die too. Even if it found a new
symbiotic partner, the partner may not provide the same nutrients in equal
amounts. When forests are just getting established, this change could have
bigger impacts because young trees cannot process as much water compared to
older trees. Having drought-resistant fungi in the first place is probably
better for both the plant and the fungus, because the plant will not have to
find a new friend, and the fungus doesn’t have to die. So as soon as California
gets some rain, planting some trees with C.
geophilum might help the trees tolerate drought better.

4. C. geophilum responds to different
levels of Nitrogen, sometimes not very well.

Like many
other soil fungi, C. geophilum cannot
fix free nitrogen from the air. It is able grow using ammonium (NH4+),
nitrate (NO3-), and amino acids as its nitrogen source,
but it likes to utilize ammonium the most.7 But like work, too much
available nitrogen can have a detrimental effect on the abundance of this
fungus. In a 2008 study, researchers found that as nitrogen availability
increases, C. geophilum becomes less
common on the roots of red spruce trees.5 This decrease is not
small; it drops from being present in 90% of the roots to about 50% when the
nitrogen concentration in roots doubles. In the last century, human activity
has doubled the amount of nitrogen deposited into the ground, which is expected
to continue increasing.8 Things like fertilizers and manure really
increase the amount of nitrogen in soils, and farming uses a whole lot of it. With
this ever-increasing amount of nitrogen in the world’s soil, it is possible that
C. geophilum will become less
important in plant symbiosis. This is because the plant now has an easier time
getting nitrogen without the help of C.
geophilum. It’s like going to your friends’ house all the time to see their
puppies, but then your significant other buys one for you instead. However,
other fungi aren’t at a loss. When the nitrogen availability increases, the
frequency of some other ectomycorrhizal fungi increases, but these other fungi
are not as common as C. geophilum.5
For our Midwestern friends, think about how the ectomycorrhizal fungi in your
front-yard tree will be affected when you decide to sprinkle that grass
fertilizer onto your lawn. You may get end up with a beautiful yard, but C. geophilum is hurting from losing its
friend.

On a
general level, nitrogen can also affect an ectomycorrhizal community. Another
study found that the concentration of nitrogen in the soil also affects how
fast different ectomycorrhizal fungi decompose when they die.4 For C. geophilum, the biomass decays about
35% in one month, which was less decomposition than the other ectomycorrhizal
fungi that were tested. These other fungi also had a higher concentration of
nitrogen in their tissues, possibly meaning that a higher tissue concentration
of nitrogen resulted in a higher decomposition rate. However, an increased
nitrogen availability didn’t really change the decomposition rate of C. geophilum. In fact, it actually
decayed less than several other types of ectomycorrhizal fungi in the same
amount of time. So even though C.
geophilum gets left out of the symbiotic relationship when nitrogen levels
increase, it sticks around when it dies, almost as if it wants to guilt the
tree for leaving it behind.

There you have it: 5 things you didn’t know about C. geophilum! Do you think have learned
a ton of new things? Take the quiz and find out how much you now love and
understand C. geophilum! (Actually,
there is no quiz.)

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This blog represents the work of students from one of the few courses devoted to Eukaryotic Microbiology as a whole. This is a new experiment for this course that we hope will be a successful fusion of student learning and science communication. Enjoy, but play nice, comments are welcome but mean-spirited comments will be deleted.